Safety mechanism for computing counters



Aug. 22, 1967 L. J. SUNDBLOM SAFETY MECHANISM FOR COMPUTING COUNTERS 5 Sheets-Sheet 1 Filed May 9, 1966 mm .w I R E Wm M W D L W B G 5 H N MR6 6 WN VU S M T T 0C E E S E J R S l S W L E S E A 6 R P 6 F E E E O L a E 2 i w w. m R 0 4 E m um C T R K m U 0 P A V W 5 6 W O 4 C E 4 k O E 8 3 4 4 4 p\/V K m 0 I I. EWEim 75:5 2 r J J 3 G Mmm i N 4 $5 w F 2 T L O I AC G ATTORNEYS Aug. 22, 3%? L. J. SUNDBLOM 3,337,327

SAFETY MECHANISM FOR COMPUTING COUNTERS Filed May 9, 1966 3 Sheets-Sheet INVENTOR. LEIF J. SUNDBLOM ATTORNEYS Aug. 2, 196'? L. J. SUNDBLO-M 3,337,127

SAFETY MECHANISM FOR COMPUTING COUNTERS Filed May 9, 1966 5 SheetsSheet 3 FlG 6 INVENTOR. LEIF J. SUNDBLOM m m h ATTORNEYS United States Patent ()fitice 3,337,127 Patented Aug. 22, 1967 3,337,127 SAFETY MECHANISM FOR COMPUTING COUNTERS Leif J. Sundlrlom, Castro Valley, Califi, assignor to Rockwell Manufacturing Company, San Leandro, Califi, a

corporation of Pennsylvania Filed May 9, 1966, Ser. No. 548,557 14 Claims. (Cl. 235-62) Ans: is or or run nrsctosunn This invention concerns metering computers, and more particularly a safety mechanism adapted for use in a metering computer equipped with a printing mechanism, which prevents damage to the computing mechanism in the event that the printer is left in a locked condition during a metering operation.

Although the invention described herein has utility in connection with many different kinds of mechanical mechanisms, it is particularly adapted for use with a metering computer of the type described in the co-pending applications of Berck and Sundblom, Ser. No. 412,974, filed November 23, 1964, and entitled Computing Counter, and Ser. No. 548,718, filed May 9, 1966, and entitled Tax Computing Metering Device. Consequently, the preferred embodiment of the invention will be described herein in connection with the mechanism of the type shown in the copending applications.

In a metering computer of the type herein under consideration, the printing mechanism is operated by an actuator knob discussed in more detail hereinafter. Since this actuator knob is operated by hand, it is conceivable that it might be left in an intermediate position during a delivery of fluid which the computer meters. Whenever the printer actuator knob is in an intermediate position, however, the nature of the printing mechanism requires that the computer mechanism be locked against rotation so as to avoid a feed-back of motion into the computing mechanism when the printing wheels of the printer are operated during the printing operation. In the co-pending application entitled Tax Computing Metering Device, this locking mechanism is schematically indicated in FIG. 3 by the symbol L. Physically, this locking mechanism consists of a brake which engages one of the wheels of the computing mechanism and holds it against rotation. While the computing mechanism is locked, the printing wheels can nevertheless move because they are connected to the computing mechanism by an appropriate ratchet clutch symbolically shown in FIG. 3 of the co-pending application entitled Tax Computing Metering Device.

With this background in mind, it will be seen that a problem arises when the printer actuator knob is left in an intermediate position in which the computer mechanism is locked, and an attempt is then made to drive the computing mechanism by delivering fluid through the metering device. In this condition (or, for that matter, in the event of any internal breakdown), the motion input to the meter must become jammed, or else there must be some intern-a1 disconnection. In either event, the delivery during which this happens will not be registered. In case of an internal breakdown, this isunavoidable; but if the trouble is caused by a mid-setting of the actuator knob, an avoidable humanerror problem is present.

The present invention solves this problem by providing a locking or braking mechanism for the computer which is automatically released when the rotational torque at the input to the computing mechanism exceeds a predetermined amount. The releasing of the brake by this safety mechanism can result in a very slight error in the indication for a particular delivery, but it positively prevents damage to the computing mechanism due to a missetting of the printer actuator knob, and furthermore maintains substantial accuracy in the registration.

It is, therefore, the object of this invention to provide a mechanism which will release the computer mechanism brake in a computing counter when the input torque exceeds a predetermined amount.

It is another object of this invention to provide a mechanism which is capable of sensing a mechanical blockage in the computer mechanism, disengaging the computer mechanism, disengaging the computer mechanism when it senses a blockage, act to relieve it, and re-engage the computer mechanism as soon as the blockage is relieved.

These and other objects of the invention will become apparent after a perusal of the following specification taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of atypical device in which the present invention is useful;

FIG. 2 is a schematic diagram showing the general method of operation of the device of this invention;

FIG. 3 is a fragmentary view showing the mechanism of this invention when the printer actuator knob is in the home position;

FIG. 4 is a view similar to FIG. 3 but showing the mechanism in a position in which the printer actuator knob has been turned clockwise out of the home position;

FIG. 5 is a view similar to FIG. 3 but showing the mechanism in the position in which the printer actuator knob has been turned 270 clockwise out of the home position;

FIG. 6 is a view similar to FIG. 3 but showing the mechanism in a position in which the printer actuator knob is in the run position;

FIG. 7 is a fragmentary view showing the mechanism in a position in which the printer actuator knob has been turned in a counter-clockwise direction from the run position to within 45 of the home position; and

FIG. 8 is a view similar to FIG. 4 but showing the position of the mechanism when the brake has been released due to the operation of the safety mechanism.

Basically, the mechanism of this invention carries out the function of locking the computing mechanism against movement at all times except when the printer actuator knob is in either the home or the run position, yet releasing the locking mechanism regardless of the position of the printer actuator knob whenever a torque limiting clutch at the input to the computer mechanism disengages as a result of an abnormal stress on the computer mechanism. At the same time, the torque limiting clutch is so arranged as to prevent damage to the mechanism even in case of an internal breakdown which cannot be remedied by the release of the braking mechanism. However, because the abnormal stress might be remedied by the release of the braking mechanism, the torque limiting clutch is arranged to momentarily re-engage at each half-revolution, and to stay engaged as soon as the torque has returned to normal.

Turning now to FIG. 1, a typical device in which the invention is useful is shown generally at 10. The computer may contain various resettable dials 12, 14, 16, a printer 18, and non-resettable counters such as 20. The printer 1-8, which may be of conventional construction, is actuated by the printer actuator knob 22. When the knob 22 is turned clockwise as far as it will go, all the resettable dials are reset to zero, and an indication of zero may be printed on an invoice inserted into the printer 18. The extreme clockwise position of knob 22 is hereinafter referred to as the run position. In this position, a delivery of fluid may take place through the metering device. At the conclusion of the delivery, the knob 22 is turned counter-clockwise as far as it will go. This movement has the effect of setting the printing wheels in the printer to an integral figure suitable for printing, and printing the delivery data onto the invoice inserted into printer 18. The extreme counter-clockwise position of knob 22 is hereinafter referred to as the home position.

FIG. 2 schematically illustrates the functioning of this invention. The motion of the metering device which meters the flow of fluid is transmitted directly to the shaft 24 which constitutes the driving means or source of rotation for the device 10. Gears 26, 28 transfer this motion directly to the non-resettable total gallonage counter 20'. Gear 30 transmits the rotation of shaft 24 to a floating gear 32 which supports the pawls 34, 36 on pivots 38, 40. The.

pawls 34, 36, as will be explained more in detail in conriection with FIG. 4 and 8 below, engage the clutch disc 42 which is keyed to shaft 44. The rotation of the clutch disc 42 is consequently transmitted to gear 46 which in turn drives gear 48. The latter constitutes the motion input to the invoice computer 50 whose operation is described in detail in the aforesaid co-pending applications. It will be understood that the invoice computer 50' has several outputs which all function in the same manner. Consequently, the schematic illustration of FIG. 2 shows only one of them. This output is represented by gear 52 which engages gear 54, to drive shaft 56.

The motion of shaft 56- is transmitted to the brake wheel 58 which can be locked by the brake 60 when the head of the brake 60 is pressed against the serrations on the surface of brake wheel 58. The brake wheel 58 i spring biased, as indicated by the arrow 62, into engagement with the floating gear 64. The brake wheel 58 and the gear 64 are provided with ratchet teeth on their sides which transmit the motion of brake wheel 58 to the gear 64 when brake wheel 58 is unlocked, but which permit the gear 64 to turn with respect to brake wheel 58 when the brake wheel 58 is locked. The motion of gear 64 is transmitted to a gear 66 which in turn drives the appropriate resettable dial or printing wheel which uses the particular output of the invoice computer 50. Parts 46 through 58 in FIG. 2 are generally referred to as the driving mechanism for the counting means, i.e. the resettable dials or printing wheels.

In FIG. 2, the lock 60 is schematically shown to be operated by a locking mechanism 68 which is normally actuated by the printer actuator knob 22 but can be released by the overstress release mechanism 70 when the sensor 72 senses an abnormal stress in the computer mechanism by virtue of the operation of the torque limiting clutch arms 34, 36. The sensor 72 is a schematic, functional representation of the sensor finger 178 described hereinafter or of equivalent mechanism. The sensing is accomplished in that 'when an abnormal stress occurs, the clutch arms 34, 36 are spread outwardly and push the finger 178 out of its normal position.

FIGS. 3 through 7 illustrate the sequence of operation of the locking mechanism 68. This mechanism consists of a brake control lever 74, a linkage 76, a control arm 78, a latching lever 80, a hammer 82, a brake arm 84, and the brake 60. The various elements of the locking mechanism 68 are operated by a main cam 86 which is keyed to the shaft 88 of control knob 22, and a floating cam 90 which has a limited range of free movement about shaft 88.

FIG. 3 shows the mechanism as it appears when the printer actuator knob 22 is in the home position. In this position, the roller 92 of the control arm 78 rests on the depressed surface 94 of the main cam 86. It is biased into this position by the spring 96 which biases the control arm 78 in a clockwise direction about its fixed pivot 98. In this position of the control arm 78, the linkage 76 (which is pivoted on control arm 78 at 100 and on the brake control lever 74 at 102) has pulled the brake control lever 74 into its most counter-clockwise position about pivot 104. The pivot 104 is mounted in an adjustable eccentric which serves as the sensitivity adjustment of the release mechanism as will be hereinafter described.

In the home position of knob 22, latch is out of latching engagement with pin 106 of control arm 78, and its surface 108 is biased into engagement with pin 106 by spring 110. Hammer 82 is in its rest position, i.e. its most counter-clockwise position about fixed pivot 112. It is held in this position by abutment of its face 114 against annular shoulder 116 of shaft 88 under the bias of spring 118.

As the computer 10 is prepared for a delivery, the knob 22 is turned clockwise from the home position to the run position, and the following occurs:

After the first of clockwise rotation of the knob 22, the parts have assumed the position shown in FIG. 4. Roller 92 has ridden up onto the elevated surface 120 of the main cam 86. This has caused control arm 78 to pivot counter-clockwise about the fixed shaft 98, bringing its pin 106 into the position shown in FIG. 4. The with drawal of pin 106 from surface 108 has caused the latch ing lever 80 to move clockwise about the fixed pin 112 to the position shown in FIG. 4, in which its clockwise movement under the influence of spring 110 is stopped by the shoulder 122 of the hammer 82. At the same time, linkage 76 has been moved to the left by the action of control arm 78, and has pushed brake control lever 74 about its pivot 104 into the position shown in FIG. 4. In this position the control face 124 of the brake control lever 74- has engaged the suface 126 of the brake arm 84 and has rotated arm 84 about the pivot shaft 98. The rotation of arm 84 is transmitted through pivot shaft 98 to brake 60, which is resiliently keyed thereto. This has caused brake 60 to pivot into the locking position where it engages the serrations on the rim of the brake wheel 58. Spring 128, which in the home position of FIG. 3 had pulled the surface 130' of brake arm 84 against stop 132, now biases the surface 126 of brake arm 184 into engagement with the shoulder 124 of the brake control lever 74. In the position of FIG. 4, the hammer 82 remains in the same position as FIG. 3 but the floating cam 90 has begun clockwise rotation due to the abutment of the face 134 of stop 136 (which is attached to shaft 88) against face 138 of stop 140 (which is attached to the floating cam 90).

-As the clockwise rotation of knob 22 continues, the condition of FIG. 5 is reached when the knob 22 has been rotated 270 from the home position. At this point, the roller 92 of control arm 78 is once again opposite the depressed surface 94 of the main cam 86. However, the control arm 78 is prevented from returning to the position of FIG. 3 by the engagement of its pin 106 with the latching surface 142 of latching lever 80. Consequently, the brake lever 84 remains in the position of FIG. 4, and the brake 60 remains engaged with brake wheel 58. In the position of FIG. 5, the floating cam 90 has been brought into a position whereit has engaged the roller 144 of hammer 82 and has pivoted hammer 82 clockwise about the pivot pin 112 against the bias of spring 118. This clockwise movement of hammer 82 has also caused the stop 122 of hammer 82 to be raised out of contact with latching lever 80, and thus latching lever 80 has been allowed to move a very slight amount in a clockwise direction under the influence of spring 1101 until its bottom surface 146 abuts against pin 106 of the control arm 78.

As the control knob continues to be rotated in a clockwise direction, the roller 144 of hammer 82 rides over the tip of the floating cam 90. Although floating cam 90 is prevented at this time from counter-clockwise rotation with respect to main cam 86 by engagement of the stop surfaces 134 and 138, there is nothing tokeep it from moving in a clockwise direction with respect to main cam 86 through a very considerable are (about 225") until its stop surface 148 hits the surface 150 of the shaft stop 136. Consequently, as the roller 144 rides over the tip of floating cam 98, the spring 118 imparts a rapid free clockwise movement to floating cam 90, in effect flipping it out of the Way. At the same time, the hammer 82 rapidly rotates in a counter-clockwise direction about pivot 112 until its surface 114 comes to rest against the shoulder 116 of shaft 88. Before this occurs, however, the stop 122 of the hammer 82 hits the surface 152 of latching lever 80 which, it will be recalled, is now in a position slightly higher than that shown in FIG. 4. The collision of stop 122 with surface 152 imparts sufficient kinetic energy to latching lever 80 to flip it in a counter-clockwise direction about pivot 112 against the bias of spring 110 far enough to free pin 106 of control arm 78 from engagement with surface 142 of the latching lever 80. Immediately, the spring 96 pulls the control arm 78 in a clockwise direction about shaft 98 to where engagement of pin 106 with surface 108 of the latching lever 80 prevents the latching lever 80 from returning into the latching position of FIG. 4. The clockwise movement of control arm 78 is stopped by engagement of roller 92 with surface 94 of the main cam 86, but not before the clockwise movement of control arm 78 has resulted in clockwise movement of the brake arm 84 under the influence of spring 128 to its position of FIG. 3 or 6 in which the brake 60 is released. Once the operation of the hammer has occurred and the brake has released, there is no further movement of the parts of the mechanism during the remaining clockwise rotation of knob 22 except for the rotation of main cam 86 to its run position shown in FIG. 6.

After completion of the delivery, the printer actuator knob 22 is returned to its home position, and the locking operation of the brake mechanism occurs in the same manner as before when the roller 92 rides up onto surface 120 of the main cam 86 and the latching lever 80 snaps into latching position. However, floating cam 90 is not drawn along with the counter-clockwise rotation of main cam 86 until stop surface 148 engages stop surface 150. After this occurs, the floating cam 98 is moved in a counter-clockwise direction until, about 35 before the knob 22 reaches home position, the roller 144 of the hammer 82 rides over the tip of floating cam 90 as shown in FIG. 7.

It will be seen from the above description that upon clockwise rotation of the knob 22, the brake 60 engages after about the first 25 of rotation and releases at the last 35 of rotation. Upon counter-clockwise rotation, the brake engages after about 90 and releases at the last 35 With the total are of rotation of knob 22 being approximately 315, this leaves an arc of about 255 (clockwise) and about 190 (counter-clockwise) during which the brake 68 locks the computing mechanism. If the metering mechanism is operated while the knob 22 is in this intermediate arc, the safety release mechanism will operate in the manner which will now be described. Incidently, the length and position discrepancy between the clockwise arc and the counterclockwise arc accounts for the necessity of providing the lathing mechanism and floating cam arrangement.

Referring to FIG. 4, it will be seen that the clutch disc 42 keyed to shaft 44 has a pair of notches at 160, 162 on its periphery. The pawls 34 and 36 are pivotable about pins 38 and 40 respectively, which in turn are mounted on gear 32 (FIG. 2) for rotation therewith. The pawls 34, 36 also have teeth 164, 166 respectively, which are normally biased into engagement with the notches 160, 162 by springs 168, 170. Normally, the tension of the springs 168, 170 is suflicient to keep the teeth 164, 166 in engagement with the notches 160, 162 so as to transmit the rotation of gear 32 to disc 42 and hence to shaft 44. If, however, the computer mechanism is locked by operation of the brake 60 or otherwise, the torque provided by the gear 32 becomes great enough to overcome the tension of the springs 168, 170, and the teeth 164, 166 ride out of the notches 160, 162. At this point, rotation of gear 32 is no longer transmitted to shaft 44. However, the departure of teeth 164, 166 from notches 160, 162 has pivoted the pawls 34, 36 about pins 38, 40 into the position shown in FIG. 8. As gear 32 continues to turn with the pawls 34, 36 in this position, the surfaces 172, 174 of pawls 34, 36 ride up against the sensor finger 178 and push it in a clockwise direction about shaft 180 against the bias of spring 182. The sensor arm 184 is keyed to the trigger arm 186 through shaft 180 and hence trigger arm 186 also rotates clockwise. This in turn causes pivot 104 to rotate clockwise about shaft,180, and in doing so it pulls brake control lever 74 up with it. Eventually, the upward movement of brake control lever 74 causes surface 126 of brake arm 84 to become disengaged from the shoulder 124, and the brake arm 84 immediately pivots clockwise about shaft 98 under the influence of spring 128 to release the brake 60 regardless of the position of the other elements of the mechanism.

As gear 32 now continues to rotate, the teeth 164, 166, at the end of a half-revolution of gear 32, drop into notches 162, 160 respectively. Since the excessive torque has now been removed by operation of the release mechanism, the torque-limiting clutch stays engaged, and the computer mechanism, having missed only a half-revolution of gear 32, continues to operate normally.

Once the safety release mechanism has operated, the brake 60 cannot be re-engaged until after the actuator knob 22 has been turned to either the home position or the run position.

The eccentric 188, which bears against surface 190 of trigger arm 186, is adjustable so as to limit counterclockwise movement of the trigger arm 186 and sensor arm 184 under the influence of spring 182 to a point where the sensor finger 178 does not quite touch the pawls 34, 36 during normal operation of the computer. The pivot 104 is also eccentrically mounted on trigger arm 186 by an adjustable eccentric 192 to permit regulation of the overlap of shoulder 124 and brake arm 84.

It will be seen that the operation of the torque limiting clutch constituted by pawls 34, 36 prevents damage to the mechanism even if the stoppage of the computer is not due to the engagement of the brake 60, but to other internal reasons such as a broken gear. In that case, the torque-limiting clutch simply re-engages and immediately disengages again at each half-revolution of gear 32. Consequently, it will be understood that the device of this application has many uses and may be modified without departing from the inventive concept to fit any required situation. Therefore, we do not desire to be limited by the preferred embodiment shown and described herein, but only by the scope of the following claims.

I claim:

1. In a counter:

a source of rotation, a function of whose rotation is to be counted;

a driving mechanism adapted to be rotated by said source of rotation;

resettable counting means adapted to be driven by said driving mechanism during a counting operation;

means for disconnecting said counting means from said driving mechanism during a resetting operation;

locking means for locking said driving mechanism against rotation during said resetting operation; and

safety means arranged to render said locking means inoperative when said source of rotation is actuated while said driving mechanism is locked.

2. The improvement of claim 1, in which said safety means include an expandable clutch between said source of rotation and said driving mechanism.

3. The improvement of claim 2, which further comprises brake means, and in which said locking means include an element which executes a predetermined movement during said resetting operation and in the course of said movement contacts said brake means to push said brake means into locking engagement with said driving mechanism against a continuous bias and to hold them therein during said resetting operation; and in which expansion of said clutch causes said element to be displaced to a position where it cannot contact said brake means 2 during its said movement.

4. The improvement of claim 2, in which said expandable clutch comprises a first member and a second member biased toward each other, said first member having a protrusion and said second member having a recess, said protrusion and recess being so arranged with respect to each other that they normally remain mated so as to cause said members to revolve in unison under the influence of said bias but that they are forced out of mating relation when the mutual torque of said members overcomes said bias so as to allow mutual revolution between said members through an are not exceeding 360 before re-mating.

5. The improvement of claim 4, in which said second member is a disc notched on its rim, and said first member is a pawl pivotally mounted on a pivot revolvable about said disc and biased thereagainst, said pawl having a tooth normally engaging said notch but adapted to ride up onto the rim of said disc to move said pawl radially outwardly when the torque between said disc and pawl overcomes said bias.

6. In a computing counter:

a source of rotation;

computing means adapted to be rotated by said source of rotation and arranged to provide an output rotation;

counting means disconnectably engaged with said computing means to count said output rotation;

locking means for locking said computing means against rotation under predetermined conditions when no counting operation is in progress;

an expandable clutch interposed between said source of rotation and said computing means, said clutch being arranged to disengage said computing means from said source of rotation for a period which is not continuous for more than one revolution of said source of rotation, and to be expanded during said period; and

safety means actuated by the expansion of said expandable clutch and operative to disable said locking means when so actuated.

7. The improvement of claim 6, in which said expandable clutch comprises a first member and a second member biased toward each other, said first member having a protrusion and said second member having a recess, said protrusion and recess being so arranged with respect to each other that they normally remain mated so as to cause said members to revolve in unison under the influence of said bias but that they are forced out of mating relation when the mutual torque of said members overcomes said bias so as to allow mutual revolution between said members through an are not exceeding 360 before re-mating.

8. The improvement of claim 7, in which said second member is a disc notched on its rim, and said first mem- 8 ber is a pawl pivotally mounted on a pivot revolvable about said disc and biased thereagainst, said pawl having a tooth normally engaging said notch but adapted to l'ide up onto the rim of said disc to move said pawl radially outwardly when the torque between said disc and pawl overcomes said bias.

9. The improvement of claim 7, which further comprises brake means, and in which said locking means include an element which executes a predetermined movement under said predetermined conditions and in the course of its said movement contacts said brake means to push said brake means into locking engagement with said computing means against a continuous bias and to hold them therein under said predetermined conditions; and in which expansion of said clutch causes said element to be displaced to a position where it cannot contact said brake means during its said movement.

10. A printing metering computer comprising:

computer means having a rotational output representative of a function of a quantity being metered;

a printing mechanism;

rotatable printer actuator means arranged to actuate said printing mechanism at selected times upon rotation of said printer actuator means in either direction through a predetermined arc; brake means engageable with said computer means to lock the same against rotation during at least a portion of the rotation of said printer actuator means;

engaging means operated by the rotation movement of said printer actuator means to engage said brake means near the beginning of said rotational movement;

latch means to hold said brake means position; and

latch release means operated by said rotational movement to release said latch means near the end of said rotational movement.

11. The device of claim 10, further comprising disabling means, and torque sensing means arranged to operate said disabling means when the torque necessary to drive said computer means exceeds a predetermined amount, said disabling means when operated disconnecting said brake means from said engaging means and latch means.

12. The device of claim 10, in which:

said brake means are resiliently biased out of engagement with said computer means;

said engaging means include a cam fixed to said printer actuator means, and first cam follower means including an element movable, upon operation of said engaging means against a resilient bias into an active position in which it normally pushes said brake means into engagement with said computer means;

said latch means hold said first cam follower means in said active position; and

said latch release means include a floating cam having a lost-motion connection to said printer actuator means, and second cam follower means resiliently biased toward said floating cam and having a member arranged to release said latch means by kinetic impact when said second cam follower means moves under the influence of its resilient bias.

13. The device of claim 11, in which:

said brake means are resiliently biased out of engagement with said computer means;

said engaging means include a cam fixed to said printer actuator means, and cam follower means including an element movable, upon operation of said engaging means, against a resilient bias into an active position in which it normally pushes said brake means into engagement with said computer means;

said torque sensing means is an expandable clutch; and

in the engaged 9 10 said disabling means, upon being operated by the eX- References Cited pansioi of Taidt gluten, withdraws laid ilemgnli UNITED STATES PATENTS agams a res1 1en ms 0 a pos1 1011 w ere 1 1s of contact with said brake means in said active posi- 2652527 8/1953 Mody al 235-432 tion of said cam follower means. 5 3,121,531 2/1964 Bumpus 235 58 14. The device of claim 13, in which said element once RICHARD H WILKINSON Primary Examiner. withdrawn, cannot return to its normal position under the influence of its resilient bias until said cam follower STEPHEN TOMSKY Examine means moves out of said active position. S, A, WAL, Assistant Examiner. 

1. IN A COUNTER: A SOURCE OF ROTATION, A FUNCTION OF WHOSE ROTATION IS TO BE COUNTED; A DRIVING MECHANISM ADAPTED TO BE ROTATED BY SAID SOURCE OF ROTATION; RESETTABLE COUNTING MEANS ADAPTED TO BE DRIVEN BY SAID DRIVING MECHANISM DURING A COUNTING OPERATION; MEANS FOR DISCONNECTING SAID COUNTING MEANS FROM SAID DRIVING MECHANISM DURING A RESETTING OPERATION; LOCKING MEANS FOR LOCKING SAID DRIVING MECHANISM AGAINST ROTATION DURING SAID RESETTING OPERATION; AND SAFETY MEANS ARRANGED TO RENDER SAID LOCKING MEANS INOPERATIVE WHEN SAID SOURCE OF ROTATION IS ACTUATED WHILE SAID DRIVING MECHANISM IS LOCKED. 